Caffeine Reaction Lab Report
The experiment did not contain any form of reaction mechanism since no chemical identity had been changed. The lab demonstrates the use of chemical molecular behavior to isolate a particular set of molecules. Caffeine had already existed in the leaf itself but needed to be separated from the other chemicals. Caffeine’s chemical structure is relatively similar to the nucleic acid purine in that they use nitrogen and is bicyclic but lacks an alkene, amine and an amide. Caffeine has a solubility of 67.0 g/100 mL in boiling water but tannins also boil in hot water to form catechin. Catechin cannot react with water but it can with calcium carbonate. The calcium carbonate was added into the reflux beforehand so the catechins can quickly change to form glucose and salts of gallic
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acid. Dichloromethane was used as an organic solvent which separates the caffeine from the aqueous layer. Caffeine is partially polar, which has a significant hydrophobic portion that only allows it to partially dissolve water; caffeine hydrolyzes with its atoms that have free electron pairs (Nitrogen & Oxygen).
After the 10ml of dichloromethane was added to the separatory funnel, two layers began to form. The top layer is the organic layer and contains the caffeine while the aqueous is at the bottom. The dichloromethane has a density of 1.326g/cm so it is denser than water and thus is at the bottom of the funnel. After the distillation , the Bunsen burner was used to sublimate the caffeine as the heating mantle and the water bath would take to long for it sublimate. The text book “Small scale approach to organic laboratory techniques” on pg.77 dictates that “Caffeine constitutes as much as 5% of the leaf material in tea plants.” Using that percentage, this estimates the amount of caffeine in 5 grams of tea leaves is 0.25 grams compared to the actual 0.017grams gained and 6.8% was collected from the 5 grams. This lab performance was better than the acetaminophen lab and overall cooperation of participants was surprising though one of the participants confused the reflux apparatus with the
distillation.
acid. Dichloromethane was used as an organic solvent which separates the caffeine from the aqueous layer. Caffeine is partially polar, which has a significant hydrophobic portion that only allows it to partially dissolve water; caffeine hydrolyzes with its atoms that have free electron pairs (Nitrogen & Oxygen).
After the 10ml of dichloromethane was added to the separatory funnel, two layers began to form. The top layer is the organic layer and contains the caffeine while the aqueous is at the bottom. The dichloromethane has a density of 1.326g/cm so it is denser than water and thus is at the bottom of the funnel. After the distillation , the Bunsen burner was used to sublimate the caffeine as the heating mantle and the water bath would take to long for it sublimate. The text book “Small scale approach to organic laboratory techniques” on pg.77 dictates that “Caffeine constitutes as much as 5% of the leaf material in tea plants.” Using that percentage, this estimates the amount of caffeine in 5 grams of tea leaves is 0.25 grams compared to the actual 0.017grams gained and 6.8% was collected from the 5 grams. This lab performance was better than the acetaminophen lab and overall cooperation of participants was surprising though one of the participants confused the reflux apparatus with the
distillation.